1. Field of the Invention
The present invention relates to a particulate matter concentration measuring apparatus.
2. Discussion of Background
As a known apparatus that detects the concentration of particulate matter mainly containing C (carbon) in exhaust gas from a diesel engine, Patent Document 1 discloses a particulate matter concentration measuring apparatus 20PM (PM sensor) shown in FIG. 1. The particulate matter concentration measuring apparatus 20PM has a sub-exhaust line 21A branched from an exhaust line 21; a particulate matter detection filter 22A arranged in the sub-exhaust line 21A; and a differential pressure measuring unit 22B that measures a differential pressure generated between the inlet and the outlet of the particulate matter detection filter 22A. The sub-exhaust line 21A is provided with a flow measuring unit 24 and a temperature measuring unit T1, and the particulate matter detection filter 22A is provided with a heater.
The particulate matter concentration measuring apparatus 20PM of EP1916394A1 measures a differential pressure ΔP generated between the front side and the rear side of the particulate matter detection filter 22A, a temperature T of exhaust gas in the sub-exhaust line 21A, and a flow Q2 of the exhaust gas in the sub-exhaust line 21A. Based on the differential pressure ΔP, the temperature T, and the flow Q2 thus measured, the mass PM (g/h) of particulate matter caught by the particulate matter detection filter 22A per unit time is calculated. Furthermore, based on the mass PM (g/h) of the particulate matter, the concentration PMconc (g/m3) of the particulate matter in the exhaust gas is calculated.
In addition, EP1916394A1 discloses a particulate matter catching filter (DPF: diesel particulate filter) 22 made of porous ceramics in the exhaust line 21 as a component of an exhaust gas purification apparatus 20. The sub-exhaust line 21A of the particulate matter concentration measuring apparatus 20PM is connected to the upstream side of the exhaust gas flow of the particulate matter catching filter (DPF) 22. Based on the concentration PMconc (g/m3) of the particulate matter in the exhaust gas specified and an operating status of an engine or the flow Q1 of the gas flowing in the particulate matter catching filter (DPF) 22 of the exhaust line 21, the mass PMenter full filter (g/h) of the particulate matter flowing into the diesel particulate filter (DPF) 22 is calculated.
The contents of EP1916394A1 are incorporated by reference herein.